Loading and unloading apparatus for a coating device

ABSTRACT

The invention relates to a device for loading at least one substrate ( 1 ) into a process chamber of a coating unit and unloading the at least one substrate ( 1 ) therefrom by means of a gripper ( 2 ) of a handling machine. The inventive device comprises a loading plate ( 3 ) which can be gripped by the gripper ( 2 ) and embodies a storage place for each at least one substrate ( 1 ), said storage place being formed by an edge ( 4 ) of an opening ( 5 ) that is assigned to each substrate ( 1 ). The inventive device also comprises a substrate holder ( 7 ) that is provided with a pedestal-type substrate support which is adapted to the loading plate ( 3 ) and on which the substrate plate can be placed such that some sectors of the surface of the substrate support are located at a certain gap distance from the substrate or the substrate lies in a planar manner on a sector of the surface.

This application is a continuation of pending International PatentApplication No. PCT/EP2003/007244 filed on Jul. 7, 2003 which designatesthe United States and claims priority from German Patent No. 10232731.9filed on Jul. 19, 2002.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for loading and unloading aprocess chamber of a coating device with at least one substrate by meansof a gripper and an automated handling unit.

It is known for the substrates which are to be coated to be introducedinto the process chamber of a coating device and removed from it againby means of a gripper of an automated handling unit. A CVD process canbe carried out in the process chamber. The gripper can act on thesubstrate directly. By way of example, the gripper may form a tonguewhich engages beneath the substrate. To unload the apparatus, thistongue has to be moved under the substrate. A gripper of this type canin each case only grip one substrate. Moreover, for the tongue to engagebeneath the substrate, the substrate has to be lifted off its supportingsurface slightly. For the substrate to be lifted off the substrateholder, the substrate holder has an apparatus, for example in the formof pins, which move out of the substrate surface in order to lift thesubstrate. An arrangement of this type leads to an inhomogeneity in thesupporting surface for the substrate and therefore to undesirableinhomogeneous temperatures on the substrate holder surface or over thesubstrate. Other methods for temporarily lifting the substrate whichhave been proposed in the prior art likewise have these drawbacks.

Furthermore, it has been proposed in the prior art to remove not justthe individual substrates, but rather the substrates together with thesubstrate holders, from the process chamber.

Working on the basis of this prior art, the invention is based on theobject of improving the loading and unloading of a process chamber withat least one substrate.

This object is achieved by the invention specified in the claims, amongwhich in claim 1 it is provided firstly and substantially that theapparatus has a loading plate which can be gripped by the gripper andforms a supporting location, which is formed by an edge of an openingassociated with each substrate, for each at least one substrate. Thesubstrate is therefore located above the opening during loading. Theedge of the opening supports the edge of the substrate. In a preferredconfiguration of the invention, the bottom of the opening is formed by arecess. The substrate is therefore located in a recess. The result ofthis is that acceleration forces applied to the loading plate cannotdisplace the substrate out of the supporting location. The openingassociated with each substrate may be circular, so that only the edge ofthe substrate rests on the edge of the opening. The contour of theopening is preferably similar to the peripheral contour of thesubstrate. If the substrate is substantially circular in form, theopening is likewise circular in form, but with a smaller diameter. Ifthe substrate has a rectangular or polygonal peripheral contour, theopening preferably has the same peripheral contour, but with a smallerdiameter. The loading plate per se may have a multiplicity of supportinglocations and may have a substantially circular circumferential contour.The supporting plate may have an annular collar on the rear side. Thesubstrate holder may have one or more pedestal-like substrate carriers,on each of which a supporting plate can be placed in such a manner thatsurface portions of the substrate carrier are at a gap spacing from thesubstrate or that the substrate rests flat on a surface portion. In theformer case, the heat transfer from the heated substrate holder to thesubstrate is effected by means of thermal radiation. In the latter case,the heat transfer is effected by heat conduction. The annular collarsurrounds a receiving cavity for receiving the substrate holder. Thesubstrate carrier may be an integral part of the substrate holder.However, it is preferable for the substrate carrier to be a platedriveable in rotation on a gas bearing. The supporting plate can befitted onto this plate in such a manner that it rotates with thesubstrate carrier. The loading plate can be located in a depression inthe substrate holder, in such a manner that its surface is flush withthe surface of the substrate holder. The material of the loading plateand the material of the substrate holder may be identical or similar.The annular collar may have a conically running inner wall. Thesubstrate carrier, onto which the loading plate can be placed, may forma circumferential formation of matching shape. When the loading plate isbeing placed on the substrate carrier, a self-centering action of theloading plate is then effected. The outer wall of the annular collar mayhave a circumferential groove. This circumferential groove may in turnform an annular engagement groove for a hook of the gripper to enter.The gripper may preferably have two gripper arms and a hook. The lengthof the two gripping arms may be shorter than the diameter of the loadingplate, so that as a result of the eccentric engagement of the grippingarms in the circumferential groove of the loading plate a tilting momentis produced when the loading plate is lifted. This tilting moment causesthe loading plate to tilt at the moment when it is lifted. As theloading plate tilts, the hook which has been introduced into thecircumferential groove moves into the engagement groove in the peripheryof the loading plate, so that the latter is securely held by thegripper. To ensure that the gripper, and in particular the arms and thehook, come into contact with the loading plate, the substrate holder hasat least three depressions which are open toward the edge. One of thesedepressions forms a centering opening. This opening may have trapezoidalopening walls. A centering projection of the gripper, with which thehook is also associated, moves into this centering opening. As thecentering projection moves into the centering opening, the rotatablesubstrate holder can be rotated slightly until it has reached itsoptimum orientation. This is of benefit to positionally accurate placingof the loading plate on the substrate carrier. Two passage-likecut-outs, which are open toward the edge of the substrate holder, areused for engagement of the gripping arms of the gripper during loadingand/or unloading of the process chamber with the loading plate. Theapparatus may also have an associated removal device. This removaldevice has vertical supports associated with each opening in the loadingplate. The plate can be fitted over these vertical supports. In theprocess, the vertical supports penetrate through the openings in theloading plates and thereby lift the substrates off the loading plate.The substrates are then located on the vertical supports and can becollected by the same or a different gripper in order to be fed to acassette or other intermediate loader. The vertical supports may beformed by at least three vertical pins.

The configuration described above provides an automatic loading andunloading system for one or more substrates for a coating device. Theloading and/or unloading may take place within a very short time. Theoperation can take place at process temperatures (400° C. to 1200° C.).This minimizes the times between the actual coating operations. Thesubstrates are removed from cassettes, which can hold a plurality ofsubstrates, and transported into the reactor. After coating has takenplace, the substrates are put back in the cassettes. During loading intoand unloading from the process chamber, the substrates are not grippedor clamped either on their surface or at their peripheral edges. Inparticular, there is no contact with the surface of the substrate at anytime. The entire operation can take place automatically. A furtheradvantage is that no particles are generated or transported to thesubstrate surface during loading and unloading.

To load the process chamber with a plurality of substrates, thesesubstrates are first of all, outside the chamber, automatically placedin recesses in a thin loading plate which consists of an identical orsimilar material to the substrate holder in the chamber. This loadingplate is formed in such a way that only the external periphery of thesubstrates is located in a cut-out in this plate. The bases of thesecut-outs form openings, the diameters of which are only slightly smallerthan the substrate diameters. This loading plate can be loaded by meansof the removal device. For this purpose, the releasable loading plate isfirst of all fitted over the vertical supports. Then, at least onesubstrate is placed onto the vertical supports in an accuratelypositioned manner by means of a robot arm. Then, the loading plate isdisplaced vertically upward until the substrates are resting on the edgeof the openings. Unloading is carried out in the reverse order. Theloading plate is then introduced into the process chamber by thegripper. As the centering projection described above moves into thecentering opening in the substrate holder, the substrate holder ispositioned by means of the centering projection, so that the loadingplate can be fitted accurately over the substrate carrier. The substratecarrier may be hotter than the loading plate. Then, however, heattransfer causes the loading plate to be heated up to the temperature ofthe substrate holder, with length expansion taking place in such amanner that the diameter of the loading plate is increased slightly. Onaccount of the conicity of the inner wall of the annular collar and ofthe circumferential wall, which is of matching shape, of the substratecarrier, as it heats up the loading plate slips downward into its finalposition, in which the substrates either rest flat on portions of thesubstrate carrier or are at a defined gap spacing from the surface ofthe substrate holder. The gap spacing is defined by the materialthickness of the loading plate, which rests flat on the surface of thesubstrate carrier.

On account of the centering projection, which interacts with thecentering opening in the substrate holder, the rotationally drivensubstrate holder only has to be roughly pre-positioned for loading andunloading. Precision positioning is effected by the gripper itself. Theretaining of the loading plate on the gripper is effected when the plateis tilted as it is lifted, with a hook engaging in an annular engagementgroove in the loading plate. The substantially rotationally symmetricalcircumferential contour of the loading plate makes it possible for thelatter to be gripped by the gripper independently of its rotationalposition.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are explained below on the basisof appended drawings, in which:

FIG. 1 shows a basic diagrammatic illustration of a substrate holderwith a total of three substrate carriers, onto each of which a loadingplate with a total of seven supporting locations has been fitted,

FIG. 2 shows a section on line II-II in FIG. 1,

FIG. 3 shows an enlarged illustration of the excerpt denoted by III inFIG. 2,

FIG. 4 shows an enlarged illustration of the enlarged excerpt denoted byIV in FIG. 2,

FIG. 5 shows a plan view of a loading plate held by a gripper,

FIG. 6 shows a section on the line VI-VI in FIG. 5,

FIG. 7 shows an illustration corresponding to FIG. 3 with the loadingplate lifted off the gripper,

FIG. 8 shows a perspective illustration of the loading plate held by agripper,

FIG. 9 shows a removal device with a loading plate fitted over verticalpins of the removal device,

FIG. 10 shows a second exemplary embodiment of the invention in anillustration corresponding to FIG. 3, and

FIG. 11 shows the second exemplary embodiment of the invention inaccordance with FIG. 4.

DETAILED DESCRIPTION OF THE DRAWINGS

The apparatus according to the invention is used in a CVD reactor. Areactor of this type has a process chamber in which a defined gas phasecomposition is set, so that one or more layers are deposited onsubstrates resting on a substrate holder which forms the base of theprocess chamber, the layer material being supplied via the gases of thegas phase. The process may be a VPE, MOCVD or, very generally, a CVDprocess.

The apparatus according to the invention is an auxiliary means forloading and unloading the process chamber with substrates in the form ofa loading plate 3 which, having been equipped with substrates 1 beforethe process, is introduced into the process chamber, where it remainsduring the coating process, in order to be removed again from theprocess chamber, together with the substrates, after the coating processhas been completed.

The loading plate 3 shown in the exemplary embodiments illustrated inthe figures is circular in form. A number of openings 5 are disposeduniformly on the surface of the loading plate 3. The openings 5 are ineach case located in recesses, so that they form a recessed edge 4 onwhich the edge 1′ of in each case one substrate 1 can rest. The recesseseach form a supporting location 6 for a substrate 1. The circumferentialcontour of the recess is substantially matched to the circumferentialcontour of the substrate. In the exemplary embodiment, thecircumferential contour of each supporting location 6 is accuratelymatched to the circumferential contour of the substrate 1. Therefore,the recess, like the substrate, forms a portion which is not round.However, it is provided that the recess has a circular circumferentialcontour. Then, the opening 5 which forms the bottom of the recesslikewise has a circular circumferential contour, the diameter of theopening 5 being smaller than the diameter of the substrate, in order toensure that the edge of the substrate rests on the edge 4.

On the rear side of the loading plate 3, which is thin in the innerregion, the thickness being 1 to 3 mm, in the vicinity of the edge 3″ ofthe loading plate 3, there is an annular collar 9. On its side facingoutward, the annular collar 9 forms an annular circumferential groove 18which, moreover, forms an undercut annular engagement groove 12. Theinwardly facing side of the annular collar 9, with a conically runningflank, forms the boundary of a receiving cavity. This conical flank 9′can be brought into surface contact with a matching inclined flank of asubstrate carrier 8.

In the exemplary embodiment, the substrate carrier 8 forms apedestal-like elevation and during the process floats on a gas bearingwhich, moreover, drives the substrate carrier 8 in rotation, so that theloading plate 3 which has been fitted over the substrate carrier 8rotates with it. In an exemplary embodiment which is not shown, however,the substrate carrier 8 may also be an integral part of the substrateholder 7.

The substrate carrier 8 is located in a depression 11 in the substrateholder 7. It is surrounded by a circumferential groove, into which theannular collar 9 of the supporting plate 3 can move in such a mannerthat the surface 3′ is flush with the surface 7′ of the substrate holder7. However, it is also possible for the surface 3′ if appropriate, forfluid dynamics reasons, to be raised with respect to the surface 7.

The diameters of substrate carrier 8 and annular collar 9 are matched toone another in such a manner that at process temperature the undersideof the loading plate 3 rests on the top side of the substrate carrier 8.

If a cold loading plate is placed onto a hot substrate carrier 8, theloading plate 3 is subject to thermal expansion and then slips down intoits final position.

The material of the loading plate 3 corresponds to the material of thesubstrate holder 7 or of the substrate carrier 8.

In the exemplary embodiment illustrated in FIGS. 3 and 4, the substrate1 is located at a gap spacing above the surface of the substrate carrier8, so that the substrate 1 is heated through thermal radiation.

In the exemplary embodiment illustrated in FIGS. 10 and 11, thesubstrate carrier 8 has a central elevation, on which the substrate 1rests areally. When the loading plate 3 is being placed onto thesubstrate carrier 8, the substrate 1 is lifted slightly above the edge 4of the supporting location 6. However, its edge can still be enclosed bythe edge of the recess.

The loading and unloading are carried out using a gripper 2. Thisgripper has two fork-like gripping arms 14 which can engage, by means ofgripping sections 14′, in the said annular circumferential groove 18(cf. FIG. 6). Consequently, the gripping arm 14 can engage beneath theouter edge 3″ of the loading plate 3 in order to lift the loading plate3 out of its position in the depression 11 in the substrate holder 7.For this purpose, the gripping arms 14 project into passages 17 in thesubstrate holder 7 which are open toward the edge. A centering opening15 is located between the two passages 17. The centering opening 15 hasa trapezoidal outline contour with inclined walls. As the gripper 2 isbeing moved in, a centering projection 16 penetrates into this opening15 which is open for centering purposes. A hook 13 is formed integrallyon this centering projection 16. This hook 13 enters the annularcircumferential groove 18.

To move the substrate holder 7 into the correct rotary orientation, ithas ribs/grooves, which can be optically scanned, on its circumferentialsurface. This means that the centering is possible not only bymechanical means but also by optical means.

The length of the gripping arms 14 is shorter than the diameter of theloading plate 3. Therefore, the axis A, which is defined by engagementof the gripping portions 14′ on the loading plate 3, is locatedeccentrically with respect to the diagonal M, so that a tilting momentoccurs when the loading plate 3 is lifted. The tilting of the loadingplate 3 causes the hook 13 to engage in the annular engagement groove12. As a result of this engagement, the loading plate 3 cannot slip outof the gripper 2 when the gripper executes translational movements.

The substrates 1 are picked up and put down with the aid of a removaldevice 19 indicated outside the process chamber. This removal device 19is substantially a plate which is disposed in the horizontal plane andfrom which a multiplicity of vertical supports project. Each verticalsupport comprises a total of three vertical pins 20. These threevertical pins 20 in each case penetrate through one opening 5 defining asupporting location 6. If the loading plate 3 is fitted over thevertical pins 20 in this way, the substrates are lifted out of theirsupporting locations 6 and, in the position illustrated in FIG. 9, canbe gripped by other grippers in order to be fed to cassettes or thelike. The loading of the loading plate 3 with substrates takes place inthe reverse order. The substrates are placed onto the vertical pins 20by means of a gripper (not shown) in such a manner that they are alignedabove the supporting locations 6. If the gripper 2 is then raised in thevertical direction, the substrates 1 move into the supporting locations6.

In an exemplary embodiment which is not shown, the substrate holder hasonly one substrate carrier 8, which is in the form of a pedestal. Thematerial of this substrate carrier 8 may also be joined integrally withthe substrate holder 7. In this configuration too it is provided thatthe substrate holder 8 as a whole be driven in rotation.

In a further exemplary embodiment of the invention which is notillustrated, it is provided that the loading plate 3 has only a singleopening 5 for a single substrate.

It is also possible for a purely mechanical drive to be used to drivethe substrate carrier in rotation. By way of example, the substrateholder may include a planetary gear mechanism with a toothed ring, whichhas an internal toothing and extends close to the edge, and a central,externally toothed sun wheel which is driveable in rotation, the twotoothings meshing with planet wheels, and a substrate carrier beingassociated with each planet wheel.

The apparatus according to the invention is suitable for the productionof all compound semiconductors, in particular for processes forproducing silicon semiconductors for high-k, ferroelectric and othersilicon processes. The apparatus is suitable in particular for theproduction of displays. The apparatus can be used together with one ormore robots for loading and unloading a reactor. It is possible to useboth rectangular and round substrates. The apparatus can be used withvarious automated handling units and their grippers. It is also possiblefor a metal, silicon oxide, graphite, molybdenum or other suitablematerial to be used as material for the loading plate. The apparatus canbe operated at high temperatures (over 1000°) and at low temperatures(below 600°) and at high and low process chamber pressures (0.1 to 1000mbar). The apparatus is distinguished by the fact that very shortloading times are possible. By way of example, the process chamber doesnot need to be completely cooled during loading. The automated handlingunit can be docked to the substrate holder under mechanical or opticalcontrol. The robot can interact with a plurality of process chambers. Byway of example, the loading plate can be removed from one processchamber and fed to another process chamber. It is also provided that anempty loading plate can be cleaned in a special apparatus. However, thecleaning of the loading plate may also take place in a process chamber.The cleaning can be carried out, for example, by etching. The substratescan be transported, together with the loading plate, from one processchamber into other process chambers or into an intermediate position.The apparatus can also be used in combination with inspection devices,such as FTIR or ellipsometry.

The apparatus is in very general terms suitable for any CVD process andalso for any condensation coating process. It can be used for thedeposition of metals, insulators, semiconductor layers formed from theelements of groups IV,III-II-V and from organic materials. Suitablesubstrate materials are any type of solids, in particular silicon, III-Vsemiconductors, II-VI semiconductors or insulators, such as glass. Inparticular plastic for display production can be used as substrate. Acondensation process is used especially for the production of displays.

All features disclosed are (inherently) pertinent to the invention. Thedisclosure content of the associated/appended priority documents (copyof the prior application) is hereby incorporated in its entirety in thedisclosure of the application, partly with a view to incorporatingfeatures of these documents in claims of the present application.

1. Apparatus for loading and unloading a process chamber of a coatingdevice with at least one substrate (1) by means of a gripper (2) of anautomated handling unit, which apparatus has a loading plate (3) whichcan be gripped by the gripper (2) and forms a supporting location, whichis formed by an edge (4) of an opening (5) associated with eachsubstrate (1), for each at least one substrate (1), characterized by asubstrate holder (7) having a pedestal-like substrate carrier (8) whichis matched to the loading plate (3) and onto which the substrate platecan be placed in such a manner that the substrate rests flat on asurface portion.
 2. Apparatus according to claim 1 or in particularaccording thereto, characterized in that the opening (5) is associatedwith the bottom of a recess.
 3. Apparatus according to one or more ofthe preceding claims or in particular according thereto, characterizedin that the opening associated with each substrate (1) is substantiallycircular, so that only the edge of the substrate (1) rests on the edgeof the opening.
 4. Apparatus according to one or more of the precedingclaims or in particular according thereto, characterized in that thesubstantially circular loading plate (3) has a multiplicity ofsupporting locations (6).
 5. Apparatus according to one or more of thepreceding claims or in particular according thereto, characterized by areceiving cavity, which is surrounded by an annular collar (9) formedintegrally on the rear side of the loading plate (3), for receiving thesubstrate carrier (8).
 6. Apparatus according to one or more of thepreceding claims or in particular according thereto, characterized inthat the substrate carrier (8) is driveable in rotation, in particularresting on a gas bearing (10) or mechanically, for example by means of aplanetary gear mechanism.
 7. Apparatus according to one or more of thepreceding claims or in particular according thereto, characterized inthat the loading plate (3) is located in a depression in the substrateholder (7), in such a manner that its surface (3′) is raised withrespect to the surface (7′) of the substrate holder (7).
 8. Apparatusfor loading and unloading a process chamber of a coating device with atleast one substrate (1) by means of a gripper (2) of an automatedhandling unit, which apparatus has a loading plate (3) which can begripped by the gripper (2) and forms a supporting location, which isformed by an edge (4) of an opening (5) associated with each substrate(1), for each at least one substrate (1), characterized in that theloading plate (3) is located in a depression in the substrate holder(7), in such a manner that its surface (3′) is flush with the surface(7′) of the substrate holder (7).
 9. Apparatus according to one or moreof the preceding claims or in particular according thereto,characterized by a conically running inner wall (9′) of the annularcollar (9) and a circumferential wall of the substrate carrier (8) whichis of a matching shape.
 10. Apparatus for loading and unloading aprocess chamber of a coating device with at least one substrate (1) bymeans of a gripper (2) of an automated handling unit, which apparatushas a loading plate (3) which can be gripped by the gripper (2) andforms a supporting location, which is formed by an edge (4) of anopening (5) associated with each substrate (1), for each at least onesubstrate (1), the gripper having two gripping arms (14), characterizedby an annular engagement groove (12), formed by the outer wall of theannular collar, for the engagement of a hook (13) of the gripper (2),the length of the gripping arms (14) being shorter than the diameter ofthe loading plate (3), so that as a result of the eccentric engagementof the gripping arms (14) in a circumferential groove of the loadingplate a tilting moment which is produced when the loading plate (3) islifted allows the hook (13) to move into the engagement groove (12). 11.Apparatus according to claim 10 or in particular according thereto,characterized by a centering opening (15), associated with the edge ofthe substrate holder (8), for a centering projection (16), which carriesthe hook (13), of the gripper (2) to enter, and/or an optical apparatusfor centering the substrate holder (7).
 12. Apparatus according to oneor more of the preceding claims or in particular according thereto,characterized by passages (17) which are open toward the edge (8′) ofthe substrate holder for the gripping arms (14) of the gripper (2) toenter.
 13. Apparatus according to one or more of the preceding claims orin particular according thereto, characterized in that the material ofthe loading plate (3) and the material of the substrate holder aresubstantially identical.
 14. Apparatus for loading and unloading aprocess chamber of a coating device with at least one substrate (1) bymeans of a gripper (2) of an automated handling unit, which apparatushas a loading plate (3) which can be gripped by the gripper (2) andforms a supporting location, which is formed by an edge (4) of anopening (5) associated with each substrate (1), for each at least onesubstrate (1), characterized by a removal device (19), which interactswith the loading plate (3), with vertical supports (20) associated witheach opening (5), over which supports the loading plate (3) can befitted in order for the substrates (1) to be removed from the loadingplate (3).
 15. Apparatus according to claim 14 or in particularaccording thereto, characterized in that the vertical supports areformed by in each case at least three vertical pins (20).
 16. Apparatusaccording to one or more of the preceding claims or in particularaccording thereto, characterized in that one or more robots areassociated with the apparatus.
 17. Apparatus according to one or more ofthe preceding claims or in particular according thereto, characterizedin that a plurality of process chambers are associated with theapparatus, it being possible for the substrates, resting on a loadingplate (3), to be moved from one process chamber into another processchamber.
 18. Apparatus according to one or more of the preceding claimsor in particular according thereto, characterized in that the apparatushas analysis devices, such as FTIR or ellipsometry.
 19. Apparatusaccording to one or more of the preceding claims or in particularaccording thereto, characterized by one or more cooling and/or heatingstations.
 20. Apparatus according to one or more of the preceding claimsor in particular according thereto, characterized by an orientationstation for orienting the loading plate (3).
 21. Apparatus according toone or more of the preceding claims or in particular according thereto,characterized in that the substrate holder (7) has rotation monitoringgrooves for determining its rotational speed and rotary position. 22.Use of an apparatus according to one or more of the preceding claims, ina manufacturing process for the deposition of semiconductor layers onsemiconductor substrates.
 23. Use of an apparatus according to claim 21or in particular according thereto, characterized in that the apparatusis used to produce a display.
 24. Use of an apparatus according to oneor more of the preceding claims or in particular according thereto,characterized in that the device is used in very general terms for a CVDprocess or a condensation coating process, and in particular for thedeposition of semiconductor layers formed from elements of groupsIV,III-V,II-VI, metals, insulators, in particular dielectrics andorganic substances on silicon substrates, II-V substrates, II-VIsubstrates, or insulators, such as glass or plastic.
 25. Use of anapparatus according to one or more of the preceding claims or inparticular according thereto, characterized in that the apparatus isoperated with hydrogen and/or nitrogen.
 26. Use of an apparatusaccording to one or more of the preceding claims or in particularaccording thereto, characterized by an integrated, automatic cleaningprocedure for the loading plate (3) in the apparatus.